The invention relates to a method for increasing the positioning accuracy of an element which is movably arranged relative to a stator, as claimed in the preamble of the independent patent claim.
In many fields of application, there is a need to be able to accurately position a moving element which can move relative to a stationary partxe2x80x94a stator. In motors, in particular in linear motors, many fields of use require the capability to move the armature to a specific position with high accuracy. This requirement for high positioning accuracy contrasts with the manufacturing tolerances of the individual components, in the quoted example of a linear motor; these being the manufacturing tolerances on the stator side and the manufacturing tolerances for the armature and for its components.
While the manufacturing tolerances on the stator side can still be measured relatively well and can be taken into account in an appropriate manner, for example in the processor or electronics of the linear motor, this is feasible only with very major effort in the case, for example, of inhomogeneously magnetized magnets in the armaturexe2x80x94if at all. Frequently, however, the errors between the position of the armature and the nominal position, which are caused by inhomogeneous magnetization of the individual magnets in the armature, are considerably more dominant than those which are caused by the manufacturing tolerances in the stator, and the tolerances on the stator side can in any case actually be measured and compensated for.
FIG. 1 shows an illustration of an example of the profile of the error between the actual position of the armature of a linear motor and its nominal position in the form of a graph, with the error between the actual position of the armature and its nominal position being plotted on the ordinate, and the nominal position of the armature being plotted on the abscissa. In this example, it can be seen that the errors in the actual position of the armature in some cases amount to more than 0.5 mm in the region of a nominal position of 30 mm (that is to say the armature has moved through about 30 mm), and in the nominal position range around about 120 mm. In general, it can be seen from this example that the error between the actual position of the armature and its nominal position may be quite considerable, especially if one considers the fact that, in certain fields of operation, linear motors are in some cases required to have a positioning accuracy which allows a typical error of only 0.1 mm.
Thus, even if it were possible to measure the specific error from the nominal position for each linear motor and for each position of the armature, possibly in some very complex manner, in order to allow subsequent compensation during operation, this procedure would nevertheless be completely unsuitable for practical use.
The invention is intended to overcome this and to propose a method by means of whichxe2x80x94in the case of a linear motorxe2x80x94the position error of the armature can be determined in a simple manner. In general terms, it should be possible to determine the position error of the movable element in a simple way.
With regard to the method, this object is achieved by the features of the independent method claim. Particularly advantageous variants result from the features of the dependent method claims. With regard to the apparatus, the object is achieved by the features of the independent apparatus claim, and particularly advantageous developments can be found in the features of the dependent apparatus claims.